Method of recovering ammonium sulphate



` June 22`- 1926'.

F. F. MARQUARD METHOD OF RECOVRING AMMONIUM SULPHATE Filed Feb.

Pgamed- June 4a2', 1926.1

UNITED STAT-ES.

- PATrnTj OFFICE.;

r. MARQUARn, 'or' armaron, PENNSYLVANIA; l

METHOD or nEcovERING Ammonium s ULrHAfrE.:

application nx'ea' 'reemary 5, 1925. vserialize. 7,067..

[This invention relatesio the Irecovery of ammonium sulphate from by-product coke and similar gases by passing the gases con- 4'crystals and Combine witlithe ammonium sulphate as im urities.l

The sulphuric acid bath which is made up 'of Water and approximately 4to 8 per cent.

-free sulphuric acid is contained in a lead lined' saturator. The gas with, its tar and ammonia vapor, after leaving the coke ovens or other source, is cooleddownto about degrees. centigrade, during which cooling process practically all the ammonia lchloride vapors are dissolved and carried off with the ammonia gas liquor. The gas is then passed through tar extractors, to remove the last traces of tar fog, after which it is passed to the ammonia sulphate saturator.

The above are the usual steps followed in the recovery of by-products from coke oven and similar gases and will not be' further described nor illustrated.

The accompanying drawing is an elevation partly in section, showing the ammonia sulphate saturator and its associated mechanisms.

Referring more particularly to the drawings', the numeral 2 designates the gas supply conduit leading from the tar extractors, (not shown) and divided into branches 3 and 4 which enter a sulphate of ammonia saturator 5v of usual form. An outlet pipe' 6 leads from the satura'tor 5 to an acid separator 7 which serves to trap any acid carried from the sa-turator 5 by the gases. An outlet pipe 8 leads from the acid separator 7 to still other gas treating apparatus or any other point desired. The acid separator 7 is provided with a drain pipe 9 leadin back into the saturator 5 to yprovide for 51e re- 'turn of the trapped acid to theV saturator.

Acid, from any suitablesonrce, is supplied to the bath in the saturator 5, throu h the pipe 10, this pipe having a control va ve 11 thereon.

The saturator 5 1s provided with an eyector 12 adapted to remove vthe ammonium sul-` phate precipitated within the saturatorand convey 1t to a' drain table le where the 4major portion of the-bath liquoris drained" Atherefrom and returned through the drain 15-to. the.saturator.- The ammonium-sul- 4phate is adapted to' be paddledmanually or,

otherwise removed from the tablell into a centrifugal drier 16 of usual construction,

Where it is dried-and finally discharged into the conduit 17 which delivers it upon a conveyer 18 which carries it to bins or other suitable places of storage (not shown).

As the gas passes through the acid bath in the saturator 5 the ammonia vapors are combined with the acid in the bath formin@ ammonium sulphate (NHQZSOl At the same time a large portion of the pyridine vapors, which are also contained in coke oven and similar gases, are combined with the sulphuric acid of the bath, forming pyridine sulphate.

The acid bath in the saturator 5 continues to build up ammonium sulphate which remains in solution until the bath reaches a stage of saturation, after which crystals of ammonium sulphate are precipitated .and fall to the bottom of the saturator 5 from which they are lifted by the ejector 12.

During the passage of the gas through the saturato-r 5 the pyridine content ofthe gasv is also largely absorbed by the acid bath and forms pyridine sulphate.

oil which is carried off by the gases and prevent building up of pyridine sulphate in the acid bath.

It has been discoveredthat the pyridine content of the yacid bath vaffects the forma..-

tion of the crystals of ammonium sulphate-A A and also makes it diflicult 'to neutralize the dried ammonium sulphate crystals.

Theunavoidable resence of the iron sul-` phate 1n commercie sulphuric acl-d usedm` The bath4 gradually builds up with pyridine sulphate`- and after a certain strength of pydidine sulphate is attained in the bath, a portion ormin the acid bath also has an objection'- able in uenceo'n the quality of the ammonia sulphate'produced inthe acid bath in lthe saturatcr, due to the iron sulphate in solucally making the acid bath slig tion reactin with the ammonia, hydrogen sulphide an cyanide in the gas and forming ferrie sulphide and ferro-ferri cyanide which is a black precipitatediscoloring the ammonia sulphate. It has also been discovered that when the acid bath is periodically made slightly alkaline, the iron in the acid bath is precipitated and may be carried off with .the tar or more thoroughly removed by filtering the bath. Y

In carrying out tly alkaline so as to depyridinize it and precipitate at least "a major portion of the iron, as ferroferri cyanide, the acid supply to the bath, is periodically cut off and the gaswith its ammonia vapors is allowed to continueto pass through the saturator until the bath becomes slightly alkaline. As the alkaline stage ot the bath is reached the -pyridine sulphate is separated into pyridine, which is carried o' mechanically by the gas, and the iron, as' ferro-ferri cyanide and ferrie sulphide, is precipitated. The ferrie sulphide and ferroferri cyanide whichare precipitated when the bath is made alkaline, combine with the tarry matter that comes tothe surface o the bath and may be either skimmed ,off or y filtered out.

lstood that this invention provides a novel From the above it'will bereadily understep thatmay be readily applied to any of the usual methodsof recovering ammonium sulphate from by-product coke and similar gases, in which the gases are lpassed through a saturator acid bath, which will eliminate in a simple and eiiicient manner the pyridine and iron content of said baths, and therefore provide for the precipitation of commercially pure ammonium sulphate.

While one specific method of renderingthe., novel stepl ofperiodil 'through a sulphuric acid bath and periodicallymaking said bath slightly alkaline, to thereby depyridinize the bath and precipitate any ferrie sulphide and ferro-ferri cyanide therein. I

3. In the recovery of ammonium sulphate from gases distilledfrom the steps which consist in passing the gases through, a sulphuric acid bath until said bath becomes saturated and crystals form and are precipitated, periodically rendering said bath suficiently alkaline to separate the pyridine sulphate content of the bath into pyridine v oil, and carrying off the oil, by the gases passing through the bath, and precipitatingv the iron as a cyanide, to be carried into the tar of the bath.

4. In the recovery of ammonium sulphate from gases distilled from coal,the steps consisting in p-assing such gases through a sulphuric acid bath until said bath becomes saturated and crystals form and are precipitated, making additionsot` acid suiiicient to maintain said bath acid and stopping said acid supply at predetermined intervals and allowing 4the passage of the gasesthrough the bath to lcontinue until said bath becomes suiiiciently alkaline ,to separate the pyridine sulphate therein into pyridine oil, which will be carried off bthe gases passing through the bath, an precipitate 4iron in the bath as a ferro-ferri cyanide into thetar with which it will be readily taken up, and .then continuing the normal operation by further additions 'of acid to said bath after each. time it is vmade alkaline.

5. In the recovery of ammonium sulphate lfrom gases distilled from coal, the steps con- `sistng in passing such gases through a sul'- phuric acid bath, and periodically neutralizing said bath while continuing the passage of the gases therethrough, to thereby depyridinize the bath.

In testimony whereof I have hereunto set myhand. p

FRANK F. MARQUARD. 

